There have BEEN splits in the past, so why should we think the future will be any different?
I would hope that so many people looking up to their founder, Archbishop Lefebvre, a man who stood up for the truth against error, that some of them would imitate their founder should the need arise.
God will use the SSPX to save souls, as long as the members are faithful. That is the key point. Bishop Williamson made that point very clear. He didn't want us to idolize either the Archbishop, or the SSPX -- though they should be given proper respect for what they have done. He wanted to emphasize that WHY the SSPX is flourishing is because we HAVE THE FAITH. If we ever compromise -- and lose the purity of the Faith, then God will raise up someone else and the Church will go on.
The famous phrase of Our Lord, that God can raise up children to Abraham of the very stones -- can be applied to Catholics, Traditional Catholics, and SSPX Catholics respectively.
We won't be saved because we're Catholic, or Trad. Catholic, or SSPX-attending Catholic. It will be because we kept the Faith, and have charity (Sanctifying Grace) in our souls.